<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      /* .box1 {
        width: 100px;
        height: 100px;
        background: pink;
        float: left;
      }
      .box2 {
        width: 200px;
        height: 200px;
        background: skyblue;
        clear: both;
      } */

      .box1{
        width: 200px;
        border: 1px black solid;
      }
      .box2{
        width: 100px;
        height: 100px;
        background: skyblue;
        float: left;
      }
      .clearfix::after{
        content: 'bbb';
        display: block;
        clear: both;
      }
    </style>
  </head>
  <body>
    <!-- <div class="box1"></div>
    <div class="box2"></div> -->

    <!-- <div class="box1">
        <div class="box2"></div>
        <div style="clear: both;"></div>
    </div> -->

    <div class="box1 clearfix">
        <div class="box2"></div>
    </div>
  </body>
</html>
